The present invention relates to intravascular methods and devices for treating hollow spaces within a person's body such as aneurysms, fistulas, and other body cavities and lumens, and is particularly well adapted for the treatment of intra-cerebral aneurysms of the cerebrovascular vessels.
The use of intravascular devices for the treatment of aneurysms has received an increasing amount of attention in the past few years as both the methods and devices available for intravascular procedures have become safer. One such method involves the insertion of a foreign body, such as an occlusion coil, within the aneurysm to precipitate the formation of a clot or thrombus within to partially or completely occlude the aneurysm and thus seal off the aneurysm. This method typically poses the risk of the coil or ensuing thrombus migrating from the aneurysm to the parent artery and causing a thrombo-embolic stroke. This method is also limited to the treatment of aneurysms with small necks opening into the artery in order to ensure that the coil will remain within the aneurysm. In another approach, a plug is inserted into the neck of a saccular aneurysm to block off blood flow into the aneurysm. If the plug is not sized correctly it may fall out of the aneurysm and into the patient's vasculature. In addition, placement of such a plug necessitates intimate contact with the aneurysm, which can cause rupture of the aneurysm and hemorrhaging. Finally, attempts have been made to treat both saccular and fusiform aneurysms by deploying grafts within the vasculature and anchoring them on either side of the aneurysm. These grafts typically extend along the entire length of a fusiform aneurysm, or lie across the mouth of a saccular aneurysm, thereby completely blocking off the flow of blood to the aneurysm and relieving the pressure thereon.
One such graft is described in U.S. Pat. No. 5,693,087 for a Method for Repairing an Abdominal Aortic Aneurysm, and consists of a tube adapted to be disposed within an abdominal aortic aneurysm and having a wire woven into one end of the graft that can be expanded to sealingly engage the vessel wall. The tube is preferably made of DACRON.RTM. and other polyester materials, TEFLON.RTM., TEFLON.RTM. coated DACRON.RTM. and porous polyurethane. U.S. Pat. No. 5,527,355 for Apparatus and Method for Performing Aneurysm Repair discloses an aneurysm graft with an array of staples at either end having outward protruding barbs that lodge into the vessel wall. In addition, an exterior band is placed around the vessel at the positions where the barbs protrude into the vessel wall. The bands may have a VELCRO.RTM. strap or a clasp, or may be heat sealed. In yet another approach to the problem, U.S. Pat. No. 5,405,379 discloses a Self Expanding Vascular Endoprosthesis comprising a sheet of resiliently flexible biocompatible material such as polypropylene. The sheet is rolled upon itself about one of its longitudinal edges and is introduced adjacent to the aneurysm through a catheter to be expelled and expand to form a bridge isolating the aneurysm from the flow of blood.
Although potentially successful in such applications as abdominal aortic aneurysms, such devices do present a few drawbacks, especially in applications such as intracranial aneurysms. Among the more notable of the difficulties presented is the need to fit such devices through a very small delivery lumen along a typically very tortuous pathway. In addition, the longer the graft the larger the surface area for clot formation and endothelial cell growth, which in extreme situations can cause new complications for the patient. Also, these devices do not have the ability to be deployed, detached and/or retrieved as would be necessary for such a device in the intra-cranial vessels. The risks posed by these devices increase in magnitude when the end organ is the brain, with its smaller vessel diameters, weaker vessel walls, and increasingly tortuous paths. The devices described above are thus less than ideally suited to intracranial intravascular intervention.
Moreover, any device placed in the parent artery of an intracranial aneurysm runs the risk of occluding perforating side branches. These perforators are small, usually less than 200 microns in diameter, and can be the sole source of blood flow to important tissues of the brain. Presently known devices such as vascular grafts and stents can easily partially or completely block the flow of blood to one or more such perforators, thereby causing clinically significant ischemic strokes.
In light of the above, it becomes apparent that there continues to be a need for a method to treat an aneurysm to minimize the risk of rupture by relieving or minimizing the stress placed upon it by the arterial blood flow with a device that can be delivered easily to an intracranial site, deployed accurately, and used by itself or in conjunction with other methods and devices to augment their efficacy.